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CLINICAL RESEARCH: HEART RHYTHM DISORDER

The Role of Left Atrial Muscular Bundles in Catheter Ablation of Atrial Fibrillation

Shih-Lin Chang, MD^_*,, Ching-Tai Tai, MD^_*, Yenn-Jiang Lin, MD^_*, Wanwarang Wongcharoen, MD^_*, Li-Wei Lo, MD^_*, Kun-Tai Lee, MD^_*, Sheng-Hsiung Chang, MD^_*, Ta-Chuan Tuan, MD^_*, Yi-Jen Chen, MD, Ming-Hsiung Hsieh, MD, Hsuan-Ming Tsao, MD^¶, Mei-Han Wu, MD, Ming-Huei Sheu, MD, Cheng-Yen Chang, MD and Shih-Ann Chen, MD^_*,_*

^_* Division of Cardiology and Cardiovascular Research Center, National Yang-Ming University, School of Medicine, Taipei, Taiwan
Radiology, National Yang-Ming University, School of Medicine, Taipei, Taiwan
Taipei Veterans General Hospital, Division of Cardiovascular Medicine, Division of Cardiovascular Medicine, Suao Veterans Hospital, Taipei Medical University, Taipei, Taiwan
Wan-Fang Hospital, Taipei, Taiwan
^¶ Division of Cardiovascular Medicine, I-Lan Hospital, Taipei, Taiwan.

Manuscript received February 16, 2007; revised manuscript received May 1, 2007, accepted May 21, 2007.

^_* Reprint requests and correspondence: Dr. Shih-Ann Chen, Division of Cardiology, Veterans General Hospital-Taipei, 201 Sec. 2, Shih-Pai Road, Taipei, Taiwan. (Email: epsachen{at}ms41.hinet.net).

Objectives: We sought to investigate the imaging of the left atrial (LA) muscular bundle and the relationship between the bundle and inducibility of tachyarrhythmia after pulmonary vein isolation (PVI).

Background: Noninducibility is used as a clinical end point of atrial substrate ablation after PVI. However, little is known about the role of the LA muscular bundles in tachyarrhythmia after PVI.

Methods: Forty-three consecutive patients with paroxysmal atrial fibrillation who underwent catheter ablation were included. Bi-atrial isochronal mapping was performed with the NavX system (St. Jude Medical Inc., St. Paul, Minnesota) during sinus rhythm. After 4 PVI, inducible organized LA flutter with or without transforming to atrial fibrillation (AF) (LA flutter/AF) was ablated with additional lines at the roof and/or mitral isthmus.

Results: The existence of bilateral muscular bundles was an independent predictor of LA flutter/AF after PVI (p = 0.02). Patients with LA flutter/AF after PVI had a greater index of the double potentials (5.4 ± 3.4% vs. 2.8 ± 1.8%, p = 0.006) and interpotential interval (33 ± 5 ms vs. 29 ± 4 ms, p = 0.02) than without LA flutter/AF. The muscular bundles were identified in 28% patients using 16-slice multidetector computed tomography, which were identical to the isochrone map. Patients with noninducible LA flutter/AF after PVI plus the additional linear ablation had a lower recurrence rate as compared with the patients without it (19% vs. 75%, p = 0.02).

Conclusions: Left atrial muscular bundles may provide a conduction block line and barrier, which is important for the formation of LA flutter/AF after PVI. The noninducibility of LA flutter/AF achieved after additional linear ablation may contribute to a better outcome in RF ablation of paroxysmal atrial fibrillation.

Abbreviations and Acronyms   CS = coronary sinus   CT = crista terminalis   DP = double potential   LA = left atrial   MDCT = multidetector computed tomography   PV = pulmonary vein   PVI = pulmonary vein isolation   RF = radiofrequency

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